This invention relates to cellular telephone apparatus and, more particularly, to apparatus normally provided at a mobile station for selectively answering an incoming call transmitted as an "alert with information" message, such that calls from different calling parties are answered differently.
When a telephone call is destined for a mobile station in a cellular telephone system, a mobile telephone switching office (MTSO) transmits calling information to a base station which services a service cell in which the mobile station is located. As is conventional, such as described in Mobile Cellular Telecommunications Systems by William C. Y. Lee, McGraw-Hill Book Company (1989), the base station, in turn, transmits a suitable control message to the mobile station over a forward control channel to command the mobile station to change over from its idle mode to an active mode. Communication from the base station to the mobile station then proceeds over a forward voice channel; and the mobile station is apprised of an incoming telephone call by means of an "alert" message transmitted thereto over the forward voice channel. The "alert" message generally includes various codes arranged as multi-bit information words to identify the type of message being transmitted, the number of words included in the message, and various other types of information that are used in cellular telephone systems. The specifics of such codes and messages are detailed in EIA standards, such as EIA/TIA-IS-54.
A typical "alert" message is intended to produce an alert, or warning, indication at the mobile station so as to apprise the user of the presence of an incoming telephone call. The typical warning indication is the generation of an audible signal, generally referred to as an audible ringing signal. Presumably, the called party, that is, the user of the mobile station, cannot distinguish between incoming calls; and the user is provided with but two options: answer or ignore the incoming call. If the mobile station is located in a vehicle, the presence of the audible ringing signal may be a distraction to the user whose concentration on operating the vehicle will be interrupted when the warning indication is generated and the call is answered.
As so often happens, the user at the mobile station may prefer not to communicate with the calling party. In other cases, voice communication with the calling party may not be needed and other responses to the incoming call may be more appropriate. However, since the user simply is provided with an audible ringing signal, the user cannot distinguish desirable calls from those which are undesired or calls which invite voice communication from those that do not. Nor can the user assess the priority of an incoming call.
It recently has been proposed to transmit additional information with the "alert" message. This additional information may be of the type which, for example, represents the importance of the incoming call, the type of call, the medium through which the call is transmitted, etc. However, a more desirable "alert with information" message would be one which includes information that identifies the calling party. In the present standard, an "alert with information" message is transmitted over a forward voice channel in "packets," with each packet including one or more multi-bit words. While several of the bits in a packet are used for control purposes, many are dedicated to identify the calling party, such as the telephone number used by the calling party to initiate the telephone call. The transmission of several words thus provides sufficient cumulative information to identify the calling party.
However, the typical use of the calling party identifying data included in the "alert with information" message has been simply to display the calling party's identity or telephone number. While this provides the user at the mobile station with additional information on which a decision can be made as to whether the incoming telephone call should be answered, the user must observe the display before taking action. Thus, the incoming audible ringing signal and the need to view a display still distracts the user.